Coriander / cilantro

March seems to be the right time for planting coriander (cilantro). From there, the weather cools down enough that the plants stay leafy and sweet instead of bolting to seed and going bitter. By June, you should get a good strong smell in the garden bed.

Sunflowers

Planting seeds in mid-August will give you tall flowers with plump buds by mid-November. You should have a decent harvest of sunflower seeds just after Christmas.

Tomato

Tomatoes are said to be a summer vegetable (actually a fruit), but the sunny, temperate Perth weather means you can get away with a bit of winter action. The first tomato I'd ever successfully grown was a propagated cutting taken at the end of autumn (Bunuru), then left in a spot with direct afternoon sunlight throughout the colder seasons (Djeran and Makuru).

Planting grape tomato seeds in decent soil in August should give you young green fruit in November that will turn red as the weeks pass. Just make sure they get lots of warm direct sunshine to keep them vigorous on nippy wet days.

Zucchini

Planting zucchini seeds in July/August should let you start harvesting in November/December.